Tham khảo tài liệu 'learning publishing dns in action ebook_10', công nghệ thông tin, hệ điều hành phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 10 It is improbable that the usual client would use a port other than port 53 since they would not be aware of the existence of ports 7053 and 8053. A DNS proxy is run on the firewall standard port 53 of the name server. The DNS proxy server identifies the source of queries. Based on their origins the proxy either refuses them or hands them over to the name server on port 7053 or the name server on port 8053. If the queries come from An Internet client then they are handed over to the Internet name server port 7053 in the figure An intranet client then there are two different cases. Firstly any request for a translation from the company. com domain is handed over to the intranet name server port 8053 . Secondly any request for a translation of a different Internet domain is left to the DNS proxy which decides o If we want to translate the Internet on the intranet then the request is handed over to the Internet name server port 7053 . o If we do not want to translate other Internet domains on the intranet then it gives a negative response. What is interesting about this is the fact that if we do not have other for example secondary name servers then we do not even need the intranet root name server. The negative response is issued directly by the DNS proxy. An application running on the firewall such as proxy then if the request is for the company .com domain it is handed over to the intranet name server port 8053 or if it concerns a different domain it is handed over to the Internet name server port 5073 . End Remarks In this book we learned about DNS principles resolver configuration and configuration of various name servers. You must have realized that domain registration and delegation is altogether quite easy. However in spite of its comprehensibility the DNS is often a source of problems to ordinary computer users. The correct diagnosis of computer problems is similar to a correct medical diagnosis. In both cases it is important not only to reach
